Forbes contributors publish independent expert analyses and insights. Eric Mack is a reporter covering science, sustainability and space. Here's a number for you: 4oo parts per million. This year ...

The average concentration of carbon dioxide in the atmosphere is likely to rise by 2.8 parts per million to 411 ppm in 2019 – passing 410 ppm just a few years after first passing the 400 ppm mark.

The carbon dioxide concentration is unlikely to dip below the 400 ppm mark for at least several decades, even with aggressive efforts to reduce global carbon emissions, according to the WMO report ...